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Liz's Clinical Chemistry Module 3 > Acid-Base and Electrolyte Instrumentation > Flashcards

Acid-Base and Electrolyte Instrumentation Flashcards

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1
Q

General composition of indicator electrodes

A
  • Ion sensitive membrane
  • Electrolyte solution (KCl or HCl)
  • Metal wire (AgCl)
  • Metal element (silver)
  • Cable to meter
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2
Q

Purpose of ion selective electrodes

A

To generate potential to ion of interest and exclude all others

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3
Q

Measurement principle of typical pH glass membrane electrode

A

?

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4
Q

Two basic functions of reference electrode

A
  • Provide stable potential

- Complete circuit

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5
Q

Components of reference electrode

A
  • Salt bridge → allows ions to enter solution
  • Electrolyte solution w/ HIGH concentration
  • Metal salt → AgCl wire
  • Metal element → Ag
  • Cable to meter
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6
Q

Composition of saturated calomel electrodes

A

Do not use saturated calomel b/c of mercury and asbestos (carcinogens)

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7
Q

Composition of silver/silver chloride electrodes

A

Ag/AgCl is used today w/ increased concentration of KCl

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8
Q

The measurement of current or amperage created as the voltage applied to an electrochemical cell is changed (e.g., oxygen and serum glucose electrodes)

A

Voltammetry

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9
Q

MEASURING AMPHERES. That branch of electrochmistry in which a fixed charge is applied to an electrochemical cell. The charge serves as the generating or excitation signal; the response is the current measured. Molecules are oxidized or reduced at the working electrode, whose potential is controlled relative to a reference electrode.

A

Amperometry

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10
Q

A voltammetric technique in which analysis is based on current/voltage curves produced during electrolysis of a solution. (electrolysis produces chemical changes by passage of an electrical current through an electrolyte)

A

Polarography

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11
Q

Antibiotic that is used in potassium ion selective electrodes

A

Valinomycin

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12
Q

Principle of direct ion selective electrodes

A

Measures undiluted sample

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13
Q

Principle of indirect ion selective electrodes

A

Measures pre-diluted sample

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14
Q

How does hyperproteinemia and hyperlipidemia interfere with sodium concentrations on both ion selective electrodes?

A

Interferes w/ both

- Indirect is more affected by both b/c fat makes sample a smaller amount

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15
Q

How can you correct for lipemia when sodium is affected?

A

Ultracentrifuge

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16
Q

Essential components of a blood gas analyzer

A
  • 3 measuring electrodes (pH, pCO2, pO2)
  • Waste pump system
  • Calibration component (2 different concentrations of pH, O2, CO2)
  • Humidifying system
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17
Q

The number of hydrogen ions needed to raise or lower 1 Liter of whole blood to a pH of 7.40; excess of bicarbonate

A

Base excess

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18
Q

A whole blood sample is hemolyzed and 4 wavelengths of light pass through the sample

A

Co-Oximeter

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19
Q

What is measured w/ a Co-Oximeter?

A
  • CO Hgb
  • Oxy Hgb
  • Met Hgb
  • Reduced Hgb/total Hgb is calculated
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20
Q

Properties that depend only on the number of particles in solution, not on the nature of those particles; used in osmolality

A

Colligative properties

21
Q

Four colligative properties

A
  • Freezing point
  • Vapor pressure
  • Boiling point
  • Osmotic pressure
22
Q

Temperature at which the vapor pressure of the solid and liquid phase are the same

A

Freezing point

23
Q

Pressure at which the liquid solvent is in equilibrium with the water vapor

A

Vapor pressure

24
Q

Temperature at which the vapor pressure of the solvent reaches one atmosphere

A

Boiling point

25
Q

Pressure that allows solvent flow between a semi-permeable membrane to establish an equilibrium between compartments of different osmolality

A

Osmotic pressure

26
Q

Is freezing point increased or decreased when solute is added to solution?

A

Decreased

27
Q

Is vapor pressure increased or decreased when solute is added to solution?

A

Decreased

28
Q

Is boiling point increased or decreased when solute is added to solution?

A

Increased

29
Q

Is osmotic pressure increased or decreased when solute is added to solution?

A

Increased

30
Q

Units for osmolarity

A

mOsm/L of H2O

31
Q

Units for osmolality

A

mOsm/kg of H2O

32
Q

`Theory of operation of a freezing point depression osmometer

A

The temp of the sample chamber is slightly lowered until below freezing point at which time the stirring rod is activated to promote crystal formation. When temp stablilizes it is read as the freezing point depression.

33
Q

Essential components of a freezing point depression osmometer

A
  • Electrode in bath of ethylene glycol (antifreeze)
  • Stir wire causes immediate freezing w/ vibration
  • Thermistor probe measure heat of fusion release by formation of crystals
  • Sample cup
34
Q

The coulometric titrator consists of the ____ electrode and ____ electrode pair

A

Indicator; generator

35
Q

This electrode is made of Ag and is the coulometric part of the titrator

A

Generator electrode

36
Q

This electrode is the amperometric part of the titrator; senses end of the rxn of free Ag ions

A

Indicator electrode

37
Q

The ____ electrode senses the current and shuts down the titration when the end point is reached

A

Indicator electrode

38
Q

this electrode is immersed in a soln containing dissolved CO2 gas; the silicone rubber membrane allows the gas to pass into an internal sodium bicarbonate buffer soln. A pH indicator and reference electrode are immersed in the buffer soln. CO2 reacts with the buffer and the pH change is sensed to measure the CO2.

A

Stow and Severinghaus (pCO2 electrode)

39
Q

This electrode is immersed in a solution containing dissolved O2 gas, polypropylene membrane allows O2 to apss into the internal phosphate buffer soln; O2 then reacts with polarized platinum cathode (high sensitivity and fast response); silver anode provides the oxidizing electrode to complete the circuit.

A

Clark (pO2 electrode)

40
Q

As O2 is consumed we get a negative charge which is proportional to pCO2 in blood gas; polarographic electrode with oxidation/reduction reactions

A

Clark (pO2) electrode…shorter description

41
Q

O2 + 2 H2O + 4e- → 4 OH-

A

Oxidation reduction rxn in Clark electrode

42
Q

CO2 + H2O ↔ HCO3 + H3O

A

Changes in pH in Stow and Severinghaus electrode

43
Q

More CO2 = ______ in pH and ______ H ions in pCO2 electrode (S&S)

A

Decreased pH and increased H+

44
Q

Chemical reactions occuring because of the flow or presence of electrons. It is thus governed by the actual transfer of energy from electrons to chemicals, or the potential for such transfer. The chemicals are in contact with the electrons at surfaces or interfaces.

A

Electrochemistry

45
Q

Describes the flow of electrons through a substance, such as a solution or a wire, and is measured in amperes, or coulombs of change per second.

A

Current

46
Q

The opposition of a substance to current flow, measured in ohms

A

Resistance

47
Q

The ability to do work, the degree of electrification as compared to some standard. for current to flow, the potential applied to the system must be greater than the resistanace exhibited by that system.

A

Potential

48
Q

The measurement of the potential difference between two electrodes measured at equilibrium and with no current. the potential generated is proportional to the activity (conc) of the ion being measured.

A

Potentiometry

49
Q

A bridge of a salt soln, usually KCl, placed between the two half-cells of a galvanic cell, either to reduce the potential of the liquid junction between the solns of the two half cells to a minimum or to isolate a soln under study from a reference half-cell and prevent chemical precipitations.

A

Salt bridge

Liz's Clinical Chemistry Module 3 (7 decks)

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